The present invention relates to a process for the piecing of a yarn in an open-end spinning device as well as to a device to carry out this process.
With the high operating speeds of the spinning rotors that are in general use today piecing under operational conditions cannot be carried out or can be carried out only with difficulty. When they are carried out, the piecing joint produced does not meet the necessary requirements. For this reason, piecing takes place as a rule at a low rotational piecing speed of the spinning rotor, whereby the feeding and the drawing off of the pieced yarn from the spinning rotor is adapted to the rotational speed of the spinning rotor which runs up again to operational speeds at the latest after the piecing process (DE 2360296 A1).
Furthermore, it is a known method to maintain the rotational speed of the spinning rotor within a predetermined range of rotational speeds during the piecing process. For this purpose, a brake is assigned to the spinning rotor to be brought to bear upon the spinning rotor or to release it as a function of the measured rotational speed behavior of the spinning rotor (DE 44 03 120 A1). However, only an approximate influence can be exerted upon the rotor speed, since a change in brake application can be undertaken only as a consequence of an ascertained deviation from the rotational speed. Thus, fluctuation of the spinning rotor""s actual rotational speed around the predetermined target speed cannot be avoided.
It is a principal object of the present invention to create a possibility to control the rotor speed in a desired manner not only during the piecing process but also during the time when the rotor speed deviates from its operational speed. Additional objects and advantages of the invention will be set forth in part in the following description or may be obvious from the description, or may be learned through practice of the invention.
The above-mentioned object is attained through a process using a drive transmission device located on a service unit. By providing a drive transmission device, it is possible to drive the spinning rotor in a precise manner at a desired rotational speed, or following a desired evolution of rotational speeds, during the piecing process when the spinning rotor does not rotate at its operating speed. The drive transmission device can then remain in use until the operating speed of the spinning rotor has been reached. It is, however, also possible to deactivate it earlier, when a controlled evolution of the spinning rotor speed has been achieved through other measures.
For the drive transmission device, a driving apparatus is preferably installed on the service unit so that such a driving apparatus need not be provided separately for every open-end spinning device. The solution according to the invention is thus economical from the point of view of material requirements as well as space requirement. Thanks to the direct control of the rotational rotor speed, a very precise evolution of the rotational rotor speed is achieved.
The rotational speed of the spinning rotor is advantageously increased in a controlled manner during the piecing process. This type of control of the rotational rotor speed makes it possible to maintain this rotational speed for the piecing process at a rotational speed level or within a rotational speed range such as to lead to optimal results with respect to the piecing joint produced.
It is advantageous for the running up of the spinning rotor to its operating speed to take place in coordination with the fiber feeding of the spinning rotor and/or the drawing off of the spun yarn from the spinning rotor. For this, it can be a distinct advantage if it were not the spinning rotor but, for example, the rotational speed of the bobbin winding up the drawn-off yarn that is taken as a guiding value to which the running-up of the spinning rotor and the fiber feed are controlled, because of the different inertia of such bobbins.
It is furthermore useful if the characteristics of the fiber material to be spun and/or the characteristics of the yarn being produced are taken into account for the control of the spinning rotor speed.
Alternatively, a process can be applied according to which no driving apparatus for the spinning rotor is provided on the service unit. Rather, the spinning rotor is driven at the required speed in every work phase by means of a change in the transmission ratio between a driving apparatus located in the spinning station and the spinning rotor, the change being controlled in the service unit.
In an advantageous embodiment of the process according to the invention, the rotor speed is maintained at least substantially constant during piecing.
In another advantageous further development of the process, the drive transmission device can be presented to an element directly or indirectly connected to the spinning rotor in order to drive the rotor, instead of being presented to the spinning rotor itself
A drive transmission device connected to a control device is used to carry out the process according to the invention. By assigning a controlled drive transmission device to the spinning rotor, the latter can be driven precisely at the low speed desired for the piecing process.
In an advantageous embodiment of the device according to the invention, the drive transmission device can be associated with a controlled driving apparatus which can be designed as part of the piecing apparatus.
The piecing apparatus is provided with an actuating element in order to actuate the drive transmission device.
According to the invention, provisions can be made for the drive transmission device to be connected indirectly to the spinning rotor via one or several interposed elements during the piecing process, instead of being connected directly to the spinning rotor.
In a preferred embodiment of the invention, a friction wheel is provided, which drives the spinning rotor via an interposed supporting disk that supports the spinning rotor.
The control device is advantageously programmable. Here, a control connection between the drives of the spinning rotor, of the feed device and of a draw-off device of the pieced yarn can be provided in an advantageous further development.
It is an advantage if a device supplying a reference value for the control of the rotational speed is provided. Furthermore, a device to influence the evolution of the spinning rotor speed as a function of the characteristics of the fiber material to be spun or of the yarn to be produced can be provided.
The process and the device according to the invention make possible a precise and simple control of the rotor speed during piecing. Reliability during spinning can be increased in this manner, and the resulting piecing joint can be improved.